Conventionally, acquisition of a relationship information piece that includes two or more language expressions having a semantic relationship has been conducted. Here, “semantic relationship” refers to, for example, a causal relationship, a superordinate-subordinate relationship, or the like. Accordingly, the relationship information piece is, for example, “cause <myocardial infarction, death>”, which indicates that the cause of death is myocardial infarction, “superordinate <medicine, headache remedies>”, which indicates that the superordinate word of headache remedies is medicine, or the like. As a method for acquiring such a relationship information piece, the method disclosed in Non-Patent Literature 1 is available, for example. With Non-Patent Literature 1, for example, an expression pattern “X is a cause of Y” is used as a clue, and the relationship information piece can be acquired by obtaining X and Y portions from a document. Meanwhile, with the method using such a pattern, a problem arises in that only the relationship described using the pattern to be the clue can be acquired.
As a method for solving that problem, a method for acquiring relationship information using analogy is disclosed in, for example, Non-Patent Literature 2.